The present invention relates to crop harvesting and conditioning machines, such as mower-conditioners, of a type including a vertically floatable header located for delivering crop to the nip of upper and lower conditioner rolls and including header float or counterbalance springs which also act to resist vertical pivotal movement of the upper conditioner roll away from the lower conditioner roll.
The idea of using header float springs to bias an upper conditioner roll toward a lower conditioner roll is known. However, the structures heretofore used for accomplishng such a dual function for float springs suffer from the disadvantage that the biasing force exerted on the upper conditioner roll diminishes as the header is raised and might result in crop being conditioned to a lesser degree than is desired, as when the header is raised for turning at the end of a field, for example. Further, these known structures lack simplicity in that they use a bell crank and link series connected between each float spring and an arm vertically pivotally supporting the upper conditioner roll. Examples of these known structures are disclosed in each of U.S. Pat. No. 3,474,601 issued Oct. 28, 1969 and U.S. Pat. No. 3,797,207 issued Mar. 19, 1974.